A small faction of the larger group of 6,219 Central American migrants in Tijuana slowly and peacefully pushed within 500 feet of the U.S. border Thursday while armed Mexican federal police held a barrier near the pedestrian crossing.

Asking for more humane conditions in the overflowing Benito Juarez shelter and trying to present themselves to United States immigration authorities for asylum, the group carried white flags as they marched from the migrant camp to the foot of the U.S. pedestrian bridge, a distance of about five city blocks.

The migrants have been camped out in muddy and cramped conditions at an open-air sports arena turned into a makeshift shelter. They said they awoke Thanksgiving Day hungry, as rain worsened the already unsanitary conditions in the packed shelter.

“There are sick children here, and we are cold and hungry,” said Carlos Lopez, a Honduran who was leading the group. Lopez added it was inappropriate to shelter the women and children outside. “The whole world is watching what is happening here.”

Tijuana municipal authorities have said they are unequipped to handle the growing numbers in the caravan.

The latest counts from Mexican authorities put 6,219 migrants in Tijuana with an additional 1,669 migrants trekking toward Baja California from the Mexican states of Jalisco, Nayarit and Sinaloa.

President Donald Trump threatened on Thursday to completely shut down the border, and the $1.6 billion daily trading relationship with Mexico. He authorized military forces to use lethal force “if necessary” to defend border agents from migrants attempting to cross into the U.S.

Using a bullhorn, Lopez galvanized a group of about 150 migrants before they left by foot for the border.

“Today is a good day to present ourselves to the United States,” Lopez said in Spanish. “It’s Thanksgiving Day. In the United States, today is a vacation day.”

Meanwhile, U.S. Customs and Border Protection made it clear they weren’t taking a day off by briefly shutting down vehicle traffic at the San Ysidro Port of Entry for a “large-scale operational readiness exercise.” They are increasing enforcement presence with helicopters, additional Border Patrol agents and U.S. military troops.

A convoy of military and Border Patrol vehicles moved into place shortly before 2 p.m., and troops marched toward the vehicle inspection area. Several large Department of Homeland and CBP helicopters circled overhead during the drill, which lasted about 10 minutes.

The drill took place about three hours after the migrant caravan made their way to the pedestrian crossing on the other side of the freeway.

During the march toward the border, Mexican federal police and Edgar Corzo Sosa, the director of the National Human Rights Commission, tried convincing the migrants to turn around when they came over Puente Tijuana, a bridge connecting the Zona Norte neighborhood where many shelters are to border infrastructure.

They urged the group to apply for workers visas in Mexico, claiming thousands of jobs were available in Tijuana.